In many genetically based diseases specific mutations or deletions can result in the loss of biological activity of a protein whose function is essential for the normal lifestyle of the cell. Often times, the particular mutation results in a failure of the protein to properly fold and therefore not be delivered to its site of action inside the cell, or secreted out of the cell. It has now been established that the pathway of protein folding is dependent upon the participation of a class of proteins now referred to as molecular chaperones. While not conveying any direct information for the folding process, molecular chaperones help reduce the possibility of a protein undergoing a nonproductive folding pathway which could lead to its misfolding and/or aggregation. Proteins unable to achieve a stable folded conformation, due for example to a specific mutation, are recognized by and retained by the actions of one or members of the molecular chaperones. Thus, molecular chaperones have been suggested to act as a type of "quality control" system inside the cell, facilitating the maturation of most polypeptides but retaining those unable to adopt their biologically active conformation, likely targeting the latter for eventual degradation. Here, we will continue with our studies examining the early events of protein synthesis, and the role of different molecular chaperones in facilitating protein maturation. Particular attention will be devoted to identifying cellular components, including the hsp70 chaperone, which interact with nascent polypeptides undergoing synthesis on the ribosome. Two potential co-factors we suspect are involved in the ATP dependent reaction cycle of hsp70 with nascent and newly synthesized proteins will be identified and characterized. In a series of related studies, we will examine the role of different molecular chaperones in the synthesis of alpha and beta tubulin and their assembly into the alpha/beta heterodimer. We suspect that newly synthesized alpha and beta tubulin initially interact with the hsp70 chaperone, and then are transferred over to another chaperone, the so- called TCP-1 chaperonin, where folding and assembly of the 65 tubulin heterodimer commences. In addition, we will follow up on our studies indicating that the assembly of 6S tubulin into microtubules, either in vitro or in vivo, again involves the participation of one or members of the chaperone family. We anticipate that these studies will further define the critical roles played by molecular chaperones in the complex pathways by which cellular proteins achieve their biologically active conformation inside the cell.